Molecular spins for quantum computation

Abstract

Spins in solids or in molecules possess discrete energy levels, and the associated quantum states can be tuned and coherently manipulated by means of external electromagnetic fields. Spins therefore provide one of the simplest platforms to encode a quantum bit (qubit), the elementary unit of future quantum computers. Performing any useful computation demands much more than realizing a robust qubit-one also needs a large number of qubits and a reliable manner with which to integrate them into a complex circuitry that can store and process information and implement quantum algorithms. This 'scalability' is arguably one of the challenges for which a chemistry-based bottom-up approach is best-suited. Molecules, being much more versatile than atoms and yet microscopic, are the quantum objects with the highest capacity to form non-trivial ordered states at the nanoscale and to be replicated in large numbers using chemical tools. This Perspective discusses how chemistry can contribute to the design of robust spin systems based on mononuclear rare-earth complexes. Using these molecular nanomagnets as key examples, we illustrate the variety of paths that chemistry has recently opened for quantum technologies: from the design of molecular spin qubits with enhanced quantum coherence to the coupling of these for implementing quantum logic gates and, finally, to the integration of such molecular quantum units into devices.

Electronic spin-spin decoherence contribution in molecular qubits by quantum unitary spin dynamics

“…Among the most promising paradigms to build quantum computers, transition-metal-based magnetic molecules have been brought forward as potential qubits, thanks to their long spin-coherence times and easy tunability [6][7][8][9][10][11][12][13]. Indeed, molecular compounds represent a rather rich materials platform, where several synthetic strategies can be exploited to selectively tune specific inter-or intra-molecular interactions, with the goal of optimising the compound and extracting the basic physical picture of the dephasing.…”

Dinuclear Copper(II) Complexes Exhibiting Reversible Photochromism

“…[2,3] One possibility to achieve this is the coherent manipulation of the electronic spin within molecules. [4,5] Recent proposals suggest that molecules exhibiting two transition metal aggregates or ions, each with a pure or effective S = 1/2 spin and separated by a redox switch capable of turning on and off the magnetic interaction between them could act as a √SWAP qugate. [6,7] The latter is a 2qubit qugate that inverts the state of both qubits only if they feature opposite readings.…”

Markovian treatment of non-Markovian dynamics of open Fermionic systems

“…Open nonequilibirum systems are at the forefront of experimental and theoretical research due to the rich and complex physics they provide access to as well as due to applicational prospects of building nanoscale devices for quantum based technologies and computations [1][2][3]. Especially intriguing in term of both fundamental science and potential applications are effects of strong correlations.…”